JP2010185658A - Method and apparatus for recovering krypton and/or xenon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for recovering krypton and/or xenon. <P>SOLUTION: Krypton and/or xenon is separated crudely from a mixture including oxygen and at least one rare gas selected from a group composed of krypton and xenon in a method including steps for feeding the mixture or a mixture derived therefrom to a rare gas recovery system and separating the mixture material in the rare gas recovery system into rare gas-lean gaseous oxygen ("GOX") and rare gas-enriched product. In the method, at least about 50 mol% of the mixture is fed to the rare gas recovery system in a gaseous phase provided that, when the mixture material is separated by selective adsorption, the concentration of xenon in the mixture material is no greater than 50 times the concentration of xenon in air. One advantage of a preferred embodiment is that it can easily be retrofitted to an existing pumped-liquid oxygen cycle air separator. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates generally to the field of air separation, and more particularly to the rough recovery of at least one noble gas selected from the group consisting of krypton and xenon from an oxygen product of air separation.

  Krypton and xenon are present in air at very low concentrations, generally about 1.14 ppm and about 0.087 ppm, respectively. Both are useful gases and therefore maximizing their recovery in the air separation process is economically encouraged.

  In a typical cryogenic air distillation process, krypton and xenon concentrates in liquid oxygen (LOX) products taken from the bottom of a low pressure (LP) distillation column are much less volatile than oxygen. Therefore, the smaller the flow rate of liquid oxygen, the more concentrated the krypton and xenon in this product.

  In the low-temperature air distillation process in which the majority of the oxygen product is removed from the low pressure column in the gas phase, gaseous oxygen (GOX) is extracted in a distillation stage several above the bottom of the low pressure column, so that krypton and xenon are with the gaseous oxygen. Measures can be taken so that little is lost. These bottom guard stages are primarily used to prevent excessive loss of krypton, which is substantially more volatile than xenon. In that case, almost all of the krypton and xenon entering the air separation plant can be recovered in a liquid oxygen product which is a very small fraction of the total oxygen flow. This liquid oxygen product can then be processed to produce a purified noble gas product. If what is needed is mainly xenon products, the bottom guard stage can be removed and much of the krypton entering the plant and almost all of the xenon can still be recovered. it can.

  If the flow rate of liquid oxygen from the distillation process is much higher, for example when all oxygen is withdrawn as liquid oxygen from the distillation column to the pressure required by the pump and vaporized in the main heat exchanger, The loss of xenon is much greater even if liquid oxygen is removed from the low pressure column several stages above the liquid stream enriched in the noble gas component. Essentially all of the krypton and xenon entering the air separation plant flows down the low-pressure column into the low-pressure column sump with the descending liquid, so the extraction of the liquid is the entire liquid extracted as a product. In proportion to this, a part of krypton and xenon is taken out. This will typically lose about 30% of these useful products.

  Accordingly, it is desirable to increase the recovery of krypton and xenon from an air separation plant that draws at least a portion of the oxygen product as liquid oxygen.

  When the main oxygen product is withdrawn as vapor from the low pressure column in the plant, krypton and xenon can be recovered by treating the liquid oxygen product as described above. However, in the case of an existing liquid oxygen cycle plant that is pressurized by a pump, it is common that all oxygen products are withdrawn from the bottom of the low-pressure column. There is no flow. Therefore, since krypton and xenon are very useful, it is also desirable to be able to add a rare gas recovery system to an existing plant.

  Furthermore, it would be desirable to provide a xenon and / or krypton recovery plant that can process a feed stream enriched in noble gases from an external source.

  U.S. Pat. No. 4,805,412 (Colley, issued February 21, 1989) discloses a method and apparatus for cryogenic distillation of air with reduced krypton and xenon losses. Oxygen is withdrawn from the low pressure column of the distillation unit and fed to the main krypton column for extraction of its krypton and xenon content. The main raw material for this main krypton column is a flow of liquid oxygen, but a small flow of gaseous oxygen is also taken from the low pressure column and supplied to the krypton column without adjusting the pressure. The low pressure column and the main krypton column operate at substantially the same pressure. A part of the top vapor with reduced krypton is condensed and supplied to the main krypton tower as a descending cleaning liquid.

  U.S. Pat. No. 6,301,929 (Lochner, issued Oct. 16, 2001) discloses an air separation process for producing a rare gas-reduced liquid oxygen stream and a rare gas-enriched liquid oxygen stream. These two liquid streams are pumped to a noble gas separation column operating at gaseous oxygen product pressure. The noble gas reduced liquid oxygen stream is sent to the top of the column as reflux, and the noble gas enriched stream is sent to the lower part of the tower. A gaseous oxygen product depleted in noble gas is withdrawn from the column as a top product, and a further bottom gas stream enriched in another noble gas is withdrawn. The reboiler / condenser in the column sump is sized to vaporize almost any oxygen feed stream. Since the oxygen feed stream is liquid, the reboiler / condenser must be large to vaporize all of the feed.

  Research Disclosure No. 42517 (disclosed anonymously in September 1999) discloses an air separation method in which oxygen product is taken as liquid oxygen from a tower apparatus. This liquid oxygen stream is pumped to oxygen product pressure and split into two streams. The first stream is sent as reflux to the top of the noble gas tower and the second stream is sent to the lower part of the tower. The relative ratio of the two streams is determined so that the column can remove methane. A gaseous oxygen product with reduced noble gas is withdrawn from the noble gas column as a top product, and a bottoms liquid stream enriched with noble gas is withdrawn. The reboiler / condenser in the noble gas column sump must be sized to vaporize almost any oxygen feed stream. Since the oxygen feed stream is liquid, the reboiler / condenser must be large to vaporize all of the feed.

  German Patent Application Publication No. 1855485 (Lochner, issued on June 10, 1999) discloses an air separation method in which a low-pressure column produces liquid oxygen with reduced rare gas and enriched with rare gas. Has been. These two liquid streams are pumped to the noble gas tower, i.e. the reduced noble gas stream is sent to the top of the tower as reflux, and the noble gas enriched stream is sent to the lower part of the tower. In addition, some gaseous nitrogen (GAN) is added to the bottom of the rare gas tower to strip the liquid descending the tower. The noble gas reduced gaseous oxygen top product is returned to the low pressure column and a further liquid oxygen stream enriched in the noble gas is withdrawn.

  US Pat. No. 6,378,333 (Dray, issued April 30, 2002) discloses an air separation process in which a first liquid oxygen stream having a xenon component is sent as reflux from a low pressure column to the upper portion of a xenon concentrating column. Has been. In the xenon concentrating tower, the liquid oxygen raw material is separated into a tower bottom liquid rich in xenon and a top product of gaseous oxygen reduced in xenon. A second liquid oxygen stream having a xenon component is withdrawn from the low pressure column, pressurized and partially vaporized by heat exchange with a portion of the feed air. In general, the liquid obtained from this partial vaporization is also sent to the xenon concentrating tower as a raw material.

  US Pat. No. 5,913,893 (Gary et al., Issued June 22, 1999) discloses a method for purifying cryogenic liquids, particularly liquid helium, by filtration and / or adsorption. Although impurities are filtered / adsorbed from the liquid, they are not available as useful products.

  US Pat. No. 5,039,500 (Shino et al., Issued August 13, 1991) gasifies a small amount of liquid oxygen purge stream taken from an air separation unit (ASU) and selectively adsorbs xenon to the gas stream. Is sent through an adsorber. Xenon is recovered during the adsorber regeneration process. The xenon concentration in the purge stream is about 31 ppm, i.e. about 360 times the concentration of xenon in the air.

  In Japanese Patent Laid-Open No. 9-2808 (Takano et al., Published on Jan. 7, 1997), a small amount of liquid oxygen purge flow taken out from an air separation device is gasified and the gas flow is converted into a first adsorber (this is xenon). Are selectively adsorbed) and then passed through a second adsorber (which selectively adsorbs krypton). Xenon and krypton are recovered during the regeneration process of these adsorbers.

  It is well known that krypton and xenon are very volatile and are concentrated in oxygen liquids. Therefore, treating the liquid oxygen stream is a prerequisite in the prior art to recover krypton and xenon. Most of the prior art also provides a small oxygen purge stream in which krypton and xenon are collected so that there is less crude recovery system. The recovery of krypton and xenon from a hot product gaseous oxygen stream is not disclosed in the prior art described above.

  In the prior art method, when recovery of krypton and xenon is desired, it is generally necessary to design the low pressure column of the air separation unit so that a small amount of a rare gas rich liquid oxygen purge stream is withdrawn. Such changes significantly increase the required capital investment and the height of the low pressure column.

US Pat. No. 4,805,412 US Pat. No. 6,301,929 German Patent Application Publication No. 1855485 US Pat. No. 6,378,333 US Pat. No. 5,913,893 US Pat. No. 5,039,500 Japanese Patent Laid-Open No. 9-2808

Research Information Disclosure No. 42517

  Overcoming the disadvantages of the prior art exemplified above (and adding improvements thereby), pure products enriched with noble gases (to be further processed into purified krypton and / or xenon products) and pure It is desirable to provide an air separation method that can produce liquid oxygen products without the need for capital and operating costs of large reboiler / condensers or additional equipment such as, for example, an argon stripping tower.

  The inventors have determined that the vapor feedstock is the reflux liquid, even if the concentration of krypton and xenon in the vapor feedstock containing xenon (and usually containing krypton) is low or the vapor feedstock is at high pressure. It was found that crude xenon can be recovered by contact. Krypton can also be recovered. The recovered product may then be further processed to provide at least one purified krypton and / or xenon product. The expression "low concentration" or "low concentration" used in the context of krypton and xenon in the steam feed is lower than in the prior art purge stream, however, the krypton and xenon concentration in the steam feed is lower than in the air. Means high.

  According to the first aspect of the present invention, at least one rare gas selected from the group consisting of krypton and xenon from a mixture containing oxygen and at least one rare gas selected from the group consisting of krypton and xenon. A method is provided for recovering. This method supplies the mixture or a mixture derived therefrom to a rare gas recovery system, and separates the raw material of the mixture in the rare gas recovery system to enrich the rare gas-reduced gaseous oxygen and rare gas. To include. This method is characterized in that at least about 50 mol% of the mixture is fed in the gas phase to the noble gas recovery system. When the mixture raw material is separated by selective adsorption, the concentration of xenon in the mixture raw material is not more than 50 times the concentration of xenon in air.

  The present invention requires that a feed mixture, mostly oxygen and at least half gas, be sent to a crude noble gas recovery system. This crude noble gas recovery system may be a tower, systematic tower, heat exchanger or adsorber, but whatever the nature of the recovery system is, the krypton and / or xenon component is concentrated and the concentrated product (And purified oxygen product) is recovered. Rather than treating a small purge stream rich in krypton and xenon, a preferred embodiment of the present invention is to treat a larger gaseous oxygen stream having a lower concentration of krypton and xenon.

  Said feed is preferably at a pressure higher than the pressure of the source from which it is removed, for example the cryogenic air distillation column from which it is originally extracted. The feedstock may be vaporized oxygen obtained from a liquid oxygen cycle using an air separation pump, gaseous oxygen from the hot end of the main heat exchanger (possibly after compression), or from an oxygen pipeline But you can. Liquid oxygen may be fed to the crude recovery system to provide refrigeration and / or reflux.

  One advantage of the present invention is that it can be applied to existing plants that produce oxygen. Such a plant can be easily modified in a crude recovery system according to the present invention so that krypton and xenon in an existing oxygen product stream can be recovered without separate treatment.

  Preferably, at least 90 mol% of the mixture raw material is a gas. More preferably, the entire mixture is a gas.

  The method is applicable to the manufacture of products enriched in xenon, products enriched in krypton, and products enriched in xenon and krypton.

  The method may further include supplying a xenon enriched stream to a noble gas recovery system. This enriched stream can be at least partially gaseous, or the enriched stream can be liquid and can be removed from a cryogenic air distillation apparatus, which is usually a different device from that which produces the mixture. it can.

  The mixture may be removed from the gaseous oxygen pipeline, in which case it is usually under pressure and no further pressure will be required. Alternatively, the mixture may be pressurized before being fed to the noble gas recovery system, for example when it is removed from the low pressure column of the air separation unit.

  The method separates feed air with a cryogenic air separator (ASU) to form a nitrogen-rich overhead vapor product and liquid oxygen (LOX), and pressurizes at least a portion of the liquid oxygen to provide pressurized liquid oxygen. And at least partially evaporating at least a portion of the pressurized liquid oxygen to provide the mixture raw material. In such a method, it is preferable to vaporize all of the at least part of the pressurized liquid oxygen to produce the mixture. The pressure of the mixture raw material is preferably higher than the operating pressure of the part of the air separator that produces the liquid oxygen. The liquid oxygen stream may be divided into at least two parts, each of which is vaporized at different pressures before being fed to the noble gas recovery system.

  In one embodiment of the present invention, the rare gas recovery system is a gas-liquid contact separation device, and the method achieves separation by contacting the mixture raw material with liquid oxygen in the separation device.

  In one configuration of this embodiment, the gas-liquid contact separation device is a gas-liquid contact column without a distillation stage, and the method separates the mixture feed through liquid oxygen in the column (eg, bubbling). Including performing.

  In another embodiment, the gas-liquid contactor is a distillation system, and the process feeds the mixture to the distillation system for separation to reduce the noble gas oxygen as overhead vapor, and A product enriched with noble gases and supplying liquid oxygen as reflux to the distillation system. Preferably, the mixture is heated before being fed to the distillation system.

  Whether at least a majority of the mixture is fed into the distillation system in a gaseous state or in a liquid state, the reduced overhead product of the noble gas is condensed and increased to a higher pressure (eg, pumped) Use), and then vaporize again.

  When the gas-liquid contact separation device is a distillation system, the method uses a low-temperature air separation device to separate the raw air into overhead vapor and liquid oxygen with reduced nitrogen, and the liquid oxygen stream is taken out from the air separation device. , Pressurize at least a portion of the liquid oxygen flow to create a pressurized liquid oxygen flow, divide the pressurized liquid oxygen flow into a main portion and a secondary portion, and at least partially vaporize the main portion. It may further comprise providing the mixture and feeding the secondary portion of liquid oxygen as reflux to the distillation system. Preferably, the main part is vaporized to make the mixture. If the distillation system comprises a single distillation column, the method supplies the mixture to the column for separation into the noble gas enriched product and the noble gas reduced liquid oxygen, and the liquid oxygen Feeding the secondary part to the column as reflux.

  When the gas-liquid contact separation device is a distillation system, the method separates the raw air with a low-temperature air separation device into a nitrogen-rich top vapor and liquid oxygen, and a liquid oxygen stream is taken out from the air separation device. Pressurizing at least a portion of the liquid oxygen stream to create a pressurized liquid oxygen stream, at least a portion of the pressurized liquid oxygen stream is at least partially vaporized to provide the mixture, and the noble gas reduced tower of gaseous oxygen Condensing at least a portion of the top vapor by indirect heat exchange with a refrigerant to form a condensed top product, and supplying at least a portion of the condensed top product to the distillation system as reflux. . Preferably, all of the at least a portion of the pressurized liquid oxygen stream is vaporized to form the mixture. If the distillation system comprises a single distillation column, the method supplies the mixture to the column for separation into the noble gas enriched product and the noble gas reduced gaseous oxygen, and Feeding at least a portion of the condensed overhead product to the column as reflux may be included.

  The distillation system can include one or more distillation columns. Typically, this system has only one tower because it reduces initial capital investment, but in some situations, a system with two or three towers may be preferred.

  In one configuration of this embodiment, the distillation system includes at least one high pressure (HP) distillation column and one low pressure (LP) distillation column. The high pressure column and the low pressure column are thermally combined by a reboiler / condenser. The method includes feeding the mixture to a high pressure column where it is separated into a noble gas reduced overhead vapor and a noble gas enriched bottom liquid. The column bottom liquid enriched with the rare gas is supplied to the low-pressure column after adjusting the pressure for separation into the gaseous oxygen in which the rare gas is reduced and the product enriched in the rare gas. The noble gas reduced overhead vapor is at least partially condensed by indirect heat exchange with the noble gas enriched product to produce at least partially condensed noble gas reduced overhead product, at least a portion of which. Is fed to the high pressure column as reflux. The liquid from or derived from the high pressure column is fed to the low pressure column as reflux. Liquid oxygen may be supplied to the high pressure column as reflux. Liquid oxygen for reflux is generally produced by separation of raw air in a low temperature air separation device. Re-boiling of the high-pressure column can be performed by at least partially evaporating the column bottom liquid enriched with the rare gas by indirect heat exchange with the heating fluid.

  In another configuration of this embodiment, the distillation system includes at least one high pressure (HP) distillation column, one medium pressure (MP) distillation column, and one low pressure (LP) distillation column. The high pressure column and the medium pressure are thermally combined by the first reboiler / condenser, and the medium pressure column and the low pressure column are thermally combined by the second reboiler / condenser. The method includes feeding the mixture to a high pressure column where it is separated into a first noble gas reduced overhead vapor and a first noble gas enriched bottom liquid. The bottom liquid enriched with the first noble gas is separated into the top vapor reduced in the second noble gas and the bottom liquid enriched in the second noble gas. Supplied to the tower. The first noble gas reduced top vapor is at least partially condensed by indirect heat exchange with the second noble gas enriched bottom liquid and at least partially condensed first noble gas reduction. The top vapor is made and at least a part of it is fed back to the high pressure column. The liquid from or derived from the high pressure column is fed as reflux to the intermediate pressure column, the low pressure column, or both. The second rare gas-depleted overhead vapor is supplied to the low pressure column for separation into the rare gas-depleted gaseous oxygen and the rare gas-enriched product. The second noble gas-reduced overhead vapor is at least partially condensed by indirect heat exchange with the noble gas-enriched product and at least partially condensed. And at least a portion thereof is fed to the medium pressure tower as reflux. The liquid from or derived from the medium pressure column is fed to the low pressure column as reflux. The method can further include supplying liquid oxygen as reflux to the high pressure column. The liquid oxygen for this reflux is preferably produced by low temperature separation of the feed air.

  In yet another configuration of this embodiment, the distillation system includes at least a first distillation column and a second distillation column, the first and second columns operating at the same pressure. In this method, the mixture is supplied to a first column for separation into a rare gas-reduced gaseous oxygen and a rare gas-enriched product, and the mixture is enriched in a rare-gas-reduced gaseous oxygen and a rare gas. From the group consisting of a product enriched with noble gas from the first column and liquid oxygen. Feeding at least one selected liquid to the second column as reflux. The method may further comprise dividing the pressurized mixture stream into two equal parts and feeding one part to each column.

  In another embodiment, the gas-liquid contact separation device is at least one heat exchanger. In such an embodiment, the method supplies the mixture to the bottom of the one or each heat exchanger, and a part of the mixture ascending the passage of the one or each heat exchanger as a refrigerant. By indirect heat exchange, and contacting the ascending mixture with the descending condensed mixture to effect defragmentation separation. Preferably, indirect heat exchange takes place in the upper part of the one or each heat exchanger. The one or each heat exchanger may be reboiled by at least partially vaporizing the product enriched with the noble gas by indirect heat exchange with the first heating fluid. The method warms gaseous oxygen depleted in the noble gas to ambient temperature by indirect heat exchange with the second heating fluid in the one or each heat exchanger and condenses the heat exchange. It can further include performing above the heat exchange to make the mixture.

  In a third aspect, the rare gas recovery system is an adsorber, and the method includes contacting the mixture feedstock with a noble gas selective adsorbent material in the adsorber. This method may be either a pressure swing adsorption (PSA) method or a temperature swing adsorption (TSA) method, both of which are well known in the art.

  The concentration of xenon in the mixture raw material is 50 times or less, preferably 20 times or less, and most preferably about 5 times the concentration of xenon in the air.

  This separation is usually a crude separation, and the noble gas enriched product produces at least one product selected from the group consisting of purified xenon products, purified krypton products, and purified krypton and xenon products. Therefore, it may be further processed. Such further processing steps are well known in the art and include burning the noble gas enriched product to remove hydrocarbon compounds and further purifying the resulting product by subsequent distillation. It is included.

  In order to remove hydrocarbon compounds, carbon dioxide and / or nitrous oxide from the liquid oxygen or gaseous oxygen feed stream to the noble gas recovery unit or from the intermediate product or the final liquid oxygen or gaseous oxygen stream. At least one adsorber may be used.

  According to the second aspect of the present invention, at least one rare gas selected from the group consisting of krypton and xenon is obtained from a mixture containing oxygen and at least one rare gas selected from the group consisting of krypton and xenon. An apparatus for recovering according to one aspect is provided, the apparatus comprising a cryogenic air separation device for separating feed air into nitrogen-rich overhead vapor and liquid oxygen, and boosting at least a portion of the liquid oxygen. Pressurizing means for providing pressurized liquid oxygen, vaporizing means for vaporizing at least about 50 mol% of the pressurized liquid oxygen to provide the mixture, and reducing the rare gas by separating the mixture A rare gas recovery system for separating the gaseous oxygen and the product enriched with the rare gas.

  The rare gas recovery system may be a gas-liquid contact tower without a distillation stage. The mixture is passed (eg, bubbled) through liquid oxygen in such a column.

  The rare gas recovery system may be a distillation system. Such an apparatus may further comprise means for superheating the mixture before feeding it to the distillation system. The apparatus further includes a conduit means for supplying a portion of the pressurized liquid oxygen from the boosting means (eg, pump) to the vaporizing means, and a remaining portion of the pressurized liquid oxygen from the pump to the distillation system. And further conduit means for feeding as reflux. The apparatus further includes at least partially condensed a noble gas reduced gaseous oxygen overhead product by at least partially condensing the rare gas reduced gaseous oxygen overhead product by heat exchange with a refrigerant. And a means for supplying at least a portion of the at least partially condensed overhead product as reflux to the distillation system.

  In a preferred embodiment where the noble gas recovery system is a distillation system, the apparatus further comprises a first distillation column for separating the mixture into noble gas depleted gaseous oxygen and noble gas enriched product. A second distillation column for separating the mixture into a rare gas-reduced gaseous oxygen and a rare gas enriched product at the same pressure as the first distillation column, to supply liquid oxygen as reflux to the first distillation column And means for supplying at least one liquid selected from the group consisting of a product enriched with a rare gas from the first distillation column and liquid oxygen to the second distillation column as reflux. Can be included.

  The noble gas recovery system may be at least one heat exchanger for separating the mixture by defragmentation. The apparatus may further comprise a first heat exchange means provided in the upper part of the one or each heat exchanger for condensing the rising mixture by indirect heat exchange with the refrigerant. The apparatus further comprises a second heat, for example provided in the upper part of the one or each heat exchanger, for evaporating the product enriched with the noble gas by indirect heat exchange with the first heating fluid. Exchange means can be included. The apparatus further heats the gaseous oxygen reduced in noble gas to ambient temperature by indirect heat exchange with a second heating fluid, and therefore from the first heat exchange means of the one or each heat exchanger. Third heat exchange means provided above may be included.

It is a general | schematic explanatory drawing of the aspect of this invention whose rare gas collection | recovery system is a single distillation column. 1B is a schematic explanatory diagram of another configuration of the aspect of the present invention shown in FIG. FIG. 3 is a schematic explanatory diagram of another configuration of the embodiment of the present invention shown in FIG. 1. 2B is a schematic explanatory diagram of another configuration of the aspect of the present invention illustrated in FIG. FIG. 2 is a schematic illustration of the distillation column shown in FIGS. 1-A, 1-B, 2-A and 2-B, without an optional distillation column at the bottom of the column. It is an outline explanatory view of the mode of the present invention which has two distillation towers where the rare gas recovery system operates at different pressures. FIG. 5 is a schematic explanatory diagram of another configuration of the aspect of the present invention shown in FIG. 4. It is an outline explanatory view of an embodiment of the present invention in which a rare gas recovery system has three distillation columns and each column operates at a different pressure. It is an outline explanatory view of the mode of the present invention which has two distillation towers in which the rare gas recovery system operates at the same pressure. It is a general | schematic explanatory drawing of the aspect of this invention whose rare gas collection | recovery system is a heat exchanger. FIG. 9 is a schematic explanatory diagram of another configuration of the aspect of the present invention illustrated in FIG. 8. It is outline | summary explanatory drawing of the aspect of this invention in which a noble gas recovery system contains an adsorber.

  Referring to FIG. 1-A, liquid oxygen is withdrawn as a stream 100 from the low pressure column 10 of the two-column air separation unit. This liquid oxygen stream 100 is transferred by a liquid oxygen pump 12 to provide a pumped liquid oxygen stream 102 containing essentially all of the krypton and xenon that entered the two-column air separation unit. The krypton and xenon concentrations in this liquid oxygen are about 5 times higher than in the atmosphere because the flow 100 flow rate is typically 20% of the air separation unit feed air flow rate. The pumped liquid oxygen stream 102 is divided into two parts. The main portion 106 is vaporized by heat exchange with the compressed air stream 130 condensing in the heat exchanger 14 to a quality of at least 0.9 (ie, 90% of the flow is gas). Ideally, the main portion 106 is completely vaporized and slightly superheated. The resulting vaporized stream 108 is sent to the lower zone of a single crude noble gas recovery tower 16. A secondary portion 104 of the pumped liquid oxygen is sent to the top of column 106 as reflux. The flow rate of the reflux stream 104 is determined by the desired recovery of krypton and xenon.

  In the crude distillation column 16, reduced overhead gas oxygen extracted as stream 110 and heated in heat exchanger 14 to provide gaseous oxygen stream 112 and extracted as product stream 120 in a known process. Is separated into a column bottom liquid enriched with a noble gas that may be further purified.

  In the heat exchanger 14, the liquid oxygen stream 106 is heated by heat exchange with the compressed feed air stream 130 (although other pressurized streams such as high pressure nitrogen may be used instead). Vaporize. Most of the compressed feed air stream 130 is withdrawn from the heat exchanger 14 as a liquefied air stream 136, but a portion 132 is withdrawn from the heat exchanger 14 and liquefied by the reboiler 18 of the crude tower. This provides a further flow 134 of air. These two liquefied air streams are combined and the combined stream 138 is fed to a two-column system of air separation unit.

  It should be noted that it is not necessary for the present invention that the heating fluid for the reboiler 18 should have the same composition as the fluid condensed by the liquid oxygen boiling in the heat exchanger 14. In addition, the reboiler 18 may be provided outside the tower 16 instead of the tower reservoir as shown. Further, when the reboiler 18 is provided outside the tower 16, the liquid from the tower 16 may be directly supplied thereto, or it may be located in a container to which the liquid from the tower 16 is supplied. It should also be noted that the column 16 may not require a reboiler if the oxygen feed stream 108 is sufficiently superheated. In this case, the descending reflux liquid is mainly vaporized by reducing the overheating of the feed stream 108.

  The larger reflux flow in the column 16 more easily wash out the krypton and xenon components from the oxygen vapor for the cleaning process. As mentioned above, the stream 108 should preferably be completely gaseous. One reason for this is that any liquid in the stream 108 must be vaporized by the reboiler 18, which requires an increase in the size of the reboiler.

  The crude column 18 is shown as having two distillation sections. In the upper part, krypton and xenon are washed away from the cleaning gas by the reflux liquid. The lower part is optional and serves to increase the concentration of krypton and xenon in the bottom liquid. Although the reflux for the crude column is illustrated as being supplied by the liquid oxygen feed stream 104, this reflux source should be supplemented or replaced with a column condenser operated by a suitable refrigerant. Can do.

  Basically, column 16 does not require any distillation stages. The oxygen feed stream 108 may be bubbled through the liquid in the column 16 reservoir. Most of the xenon in the oxygen source moves to the liquid in the reservoir. When the oxygen raw material 108 has two phases, most of the xenon in the raw material is in the liquid phase. Nevertheless, in addition to the reboiler, having at least one distillation stage is highly preferred.

  An optional noble gas enriched stream 140 that may come from a distillation column different from that from which the oxygen feed stream 108 originates may be fed to the column 16. In general, stream 140, if present, may be a noble gas rich purge stream from another air separation plant and it may be a liquid or at least partially a gas. This optional noble gas enriched feed stream is applicable to any aspect of the present invention.

  The method shown in FIG. 1-B is the same as that shown in FIG. 1-A, and corresponding parts are given the same numbers.

  In the crude distillation column 16, separation is made into overhead gas oxygen with reduced noble gases and a bottom gas enriched with noble gases that are extracted as product stream 120 and can be further purified by known methods. . The overhead gas oxygen reduced in the rare gas is condensed in the overhead condenser 20. A portion 109 of the resulting liquid is returned to the distillation column 16 as reflux, and the remaining portion 111 is pumped to a high pressure (preferably above the critical point), vaporized (if below the critical point), and heat exchange. Warming in vessel 14 provides a gaseous oxygen stream 112. This warming (and vaporization (if this is done)) of this gaseous oxygen stream is mainly done in the compressed air stream 160, which is cooled (and condensed (if below the critical point)) to form a two-column air separation unit. This produces a stream 162 that is fed to the system.

  In the heat exchanger 14, the liquid oxygen stream 106 is heated and vaporized with a compressed feed or recycled air stream 130 (although other pressurized streams may be used instead, such as high pressure nitrogen, etc.). Most of the compressed air stream 130 is withdrawn from the heat exchanger 14 as a liquefied air stream 136, but a portion 132 is withdrawn from the heat exchanger 14 and liquefied with the crude tower reboiler 18 to produce a further stream 134 of liquefied air. provide. The two liquefied air streams are combined and the combined stream 137 is depressurized and fed to the top condenser 20 of the distillation column 16. Here it is partially vaporized to provide a vapor stream 150 and is heated in heat exchanger 14 to create stream 152. The remaining liquid 138 is fed to a two-column system of the air separation device. The vapor stream 152 may be compressed again to create all or part of the compressed air feed stream 130.

  It should be noted that it is not necessary for the present invention that the heating fluid for reboiler 18 should have the same composition as the liquid oxygen boiled in heat exchanger 14 or the fluid condensed by the cooling fluid for condenser 20. is there. It should also be noted that the condenser 20 need not be located in the tower, and its role may be performed by the main heat exchanger 14.

  Referring now to FIG. 2-A, a liquid oxygen stream 200 is withdrawn from the cold box 20 of the pumped liquid oxygen air separation device and is transported by the liquid oxygen pump 22 to provide a pumped liquid oxygen stream. This is divided into two parts. A major portion is vaporized in the cold box 20 to provide a hot pressurized gaseous oxygen stream 204. This stream contains most of the krypton and xenon that entered the pumped liquid oxygen air separator. The concentration of krypton and xenon in gaseous oxygen is about five times higher than in the atmosphere because the flow 200 flow rate is typically 20% of the air separation unit feed air flow rate. Gaseous oxygen stream 204 is cooled in heat exchanger 24 to provide a stream 208 having a quality of at least 0.9. Ideally, stream 208 should be superheated. Stream 208 is fed to the lower portion of a single crude noble gas recovery tower 26. The remaining portion 202 of the pumped liquid oxygen stream from pump 22 is optionally warmed in heat exchanger 29 and fed as stream 203 to the top of column 26 to provide reflux and cooling.

  In the crude distillation column 26, the reduced overhead gas oxygen removed as stream 210 and heated in heat exchanger 24 to provide gaseous oxygen product stream 212 and extracted as product stream 220 and known methods. Is separated into a column bottom liquid enriched with a noble gas that may be further purified.

  A secondary portion 230 of the compressed feed air of the pumped liquid oxygen air separator is cooled in heat exchanger 24 and cooled stream 232 is fed to reboiler 28 where it is condensed. Condensed air stream 234 is optionally returned to the pumped liquid oxygen air separator after heat exchange with liquid oxygen stream 202 in subcooler 29. The reboiler 28 may be external to the tower 26 and, if desired, in its own container. Stream 230 need not be a pressurized air stream. Any suitable boosted flow (eg, increased nitrogen) can be used to provide the reboiler 28 heating load. Further, the increased pressure flow that provides the reboiler heating load may be fed directly to the reboiler as a low temperature stream from the main air separation device 30 rather than a high temperature stream cooled by the exchanger 24. The exchanger 24 may have other streams associated therewith, for example, stream 220 may be vaporized and warmed with the exchanger before further purification.

  The flow rate of reflux stream 203 is determined by the desired recovery of krypton and xenon. As in FIG. 1, any liquid in stream 208 must be vaporized by reboiler 28, and since this requires the reboiler to be enlarged, stream 208 is preferably completely gaseous. .

  Column 26 is illustrated as having two distillation sections. In the upper part, krypton and xenon are washed out from the cleaning gas by the reflux liquid. The lower part is optional and serves to increase the concentration of krypton and xenon in the bottom liquid. Although the reflux for the crude column is shown as a liquid oxygen feed stream 203, this reflux source can be supplemented or replaced with a column condenser operated by a suitable refrigerant.

  From this figure it can be readily seen that the present invention is suitable for incorporating a krypton and xenon recovery system with a simple modification to an existing pumped liquid oxygen air separation unit. Both the gaseous oxygen stream 204 and the compressed feed air stream 230 are hot fluids and are therefore readily available for such modifications. The liquid oxygen stream 202 for reflux and cooling is easily supplied by connecting to the discharge line of the liquid oxygen pump 22 outside the cold box. The compressed air liquefied by the crude product recovery apparatus is sent as a pipe line 234 to the cold box of the air separation apparatus. It is simple to design a cold box to easily route this flow along with the main liquefied compressed feed air flow of the air separation unit. Therefore, the retrofit for installing the rare gas recovery system can be easily utilized with a minimum initial capital investment.

  The method shown in FIG. 2-B is the same as that shown in FIG. 2-A, and corresponding parts are given the same numbers. A liquid oxygen stream 200 is withdrawn from the cold box 20 of the pumped liquid oxygen air separator and a liquid oxygen pump 22 provides a pumped liquid oxygen stream which is divided into two parts. The main portion is vaporized within the cold box 20 to provide a hot pressurized gaseous oxygen stream 204, which may be at supercritical pressure. This stream contains most of the krypton and xenon that entered the pumped liquid oxygen air separation unit. The concentration of krypton and xenon in gaseous oxygen is about five times higher than in the atmosphere because the flow 200 flow rate is typically 20% of the air separation unit feed air flow rate. The gaseous oxygen stream 204 is cooled (and condensed if subcritical) in the heat exchanger 24 to provide a stream 205 that is a liquid or supercritical dense phase stream. A portion 250 of the stream 205 is mixed with the liquid oxygen stream 202 and the remaining portion 207 is depressurized and vaporized by the compressed air stream 230 that mainly condenses in the heat exchanger 24 to provide a quality of at least 0.9. 208 is formed. Ideally, stream 208 should be superheated. Stream 208 is fed to the lower portion of a single crude noble gas recovery tower 26. The remaining portion 202 of the pumped liquid oxygen stream from pump 22 is optionally warmed in heat exchanger 24 and depressurized and fed as stream 203 to the top of column 26 to provide reflux and cooling. .

  In the crude distillation column 26, the overhead gas oxygen reduced in the noble gas withdrawn as stream 210, and the bottom liquid enriched in the noble gas that is withdrawn as product stream 220 and may be further purified by known methods, Separation is made. The gaseous oxygen stream 210 is condensed in the heat exchanger 24, pressurized in the pump 23, and the pumped stream 211 is reheated (and subcritical) by the gaseous oxygen stream 204 that mainly flows in the heat exchanger 24. In some cases, it is vaporized) to provide a gaseous oxygen product stream 212. The pressure of stream 212 is similar to stream 204 and can be higher if these streams are supercritical.

  The compressed feed air stream 230 of the pumped liquid oxygen air separator is divided into two parts: a secondary part 231 and a main part 260. Stream 231 is cooled in heat exchanger 24 and cooled stream 232 is fed to reboiler 28 where it is condensed to produce stream 234. Stream 260 is cooled and condensed in heat exchanger 24 primarily by vaporizing oxygen stream 207 to form stream 262, which is mixed with stream 234 and decompressed to produce stream 264. This stream is vaporized and warmed in the heat exchanger 24 by the gaseous oxygen stream 210 condensing and the cooling air streams 260 and 261 to form a stream 266. The reboiler 28 may be external to the tower 26 and, if desired, in its own container. The return air stream 266 is at a lower pressure than the feed stream 230 and may be re-pressurized with a separate compressor (not shown) to form all or part of the stream 230, or as shown Stream 230 may be returned to the suction side of compression stage 270 after stage 268. Stream 230 is the majority of the flow rate through compressor 268, so there is little inefficiency caused by reducing the pressure in the remaining portion that goes directly to subsequent compression stage 270.

  From this figure, it can also be readily seen that the present invention is suitable for incorporating a krypton and xenon recovery system with a simple modification to an existing pumped liquid oxygen air separation device. Gaseous oxygen stream 204, compressed feed air stream 230, and return air stream 266 are all hot fluids and are therefore readily available for such modifications. The liquid oxygen stream 202 for reflux and cooling is easily supplied by connecting to the discharge line of the liquid oxygen pump 22 outside the cold box. Therefore, the retrofit for installing the rare gas recovery system can be easily utilized with a minimum initial capital investment.

  FIG. 3 shows a crude krypton and xenon recovery tower 36 similar to that used in the method shown in FIGS. The tower 36 differs from the tower of FIGS. 1 and 2 in that it omits the optional tower bottom stage.

  The main noble gas-containing oxygen feed to column 36 is stream 308 which is at least 90% gaseous. The oxygen feed is separated in column 36 into a gaseous oxygen overhead product with reduced rare gas taken off as stream 310 and a liquid oxygen tower bottom liquid enriched in rare gas taken off as stream 320. The column 36 is refluxed by a liquid oxygen stream 304 fed to the top of the column. The flow rate of the liquid oxygen reflux stream 304 determines the loss of xenon in the overhead vapor and especially of the more volatile krypton. Selection of liquid oxygen reflux / raw gas oxygen flow rate determines the liquid to vapor (L / V) flow rate ratio.

  In FIG. 3, it should be noted that stream 304 is generally a portion of the pumped liquid oxygen, thereby having the same krypton and xenon concentrations as feed gas oxygen stream 308. Thus, the overhead gaseous oxygen stream 310 is in equilibrium with the liquid oxygen stream 304 and therefore contains some krypton and xenon. Substituting stream 304 by using a tower condenser that condenses a portion of the overhead gas with a suitable refrigerant and returns it to the tower as reflux, optionally withdrawing a small portion as a liquid oxygen product with reduced noble gases, or Complementing this is within the scope of the present invention.

  Although FIG. 3 shows only a single tower portion, there may optionally be a lower portion between the feed 308 and the reboiler 38. Such additional tower portions help to concentrate krypton and xenon in the bottom product.

  A stream 332 of heating fluid, such as compressed feed air, is condensed in the reboiler 38 by the boiling liquid enriched in the noble gas in the column 36, resulting in a condensed heating fluid stream 334. It should be noted that the reboiler 38 may be eliminated if the feed stream 308 is sufficiently superheated. In this case, the refrigeration necessary to reduce the overheating of the feed stream is provided by vaporizing the falling liquid oxygen in the column so that only stream 320 remains.

  FIG. 4 shows a crude noble gas recovery system that includes a high pressure column 40 that is thermally combined with the low pressure column 42 via a reboiler 44. An oxygen feed stream 400 having a vapor quality of at least 0.9 and containing more krypton and xenon than the atmosphere is fed to the lower portion of the high pressure column 40. Ideally, the feed stream 400 is in a gaseous state.

  In the high-pressure tower 40, separation is made into a tower top vapor in which the rare gas is reduced and a tower bottom liquid enriched in the rare gas. The enriched column bottoms are withdrawn as stream 404 and fed to the lower zone of low pressure column 42 where it is removed as stream 408 and further processed if necessary to provide purified krypton and / or xenon products. It is separated into a noble gas reduced product and a noble gas enriched overhead vapor that is withdrawn as stream 406. The overhead vapor from the high pressure column 40 is at least partially condensed in the reboiler 44 by heat exchange with the noble gas reduced boiling product to provide an at least partially condensed overhead product. A portion of this condensed overhead product is used as reflux for the high pressure column 40 and the remainder is fed to the low pressure column 42 as reflux for stream 402. A portion of stream 402 can optionally be withdrawn as a noble gas reduced liquid oxygen product with stream 412.

  Generally, the flow rate of stream 402 is approximately half of the flow rate leaving reboiler 44, so the L / V ratio in both columns is similar. This L / V ratio is about 0.5 when the oxygen feed stream is all steam as preferred. The higher the L / V ratio, the more difficult it is for xenon and especially krypton to escape from this tower system.

  The pressure difference between the two towers tends to be small because the fluid composition on both sides of the reboiler is similar. Therefore, there is a problem to be considered regarding the liquid transfer from the high pressure column 40 to the low pressure column 42. One or more pumps may be required to perform this transfer. Alternatively, gaseous oxygen vapor may be introduced into the transfer line, thereby transferring the liquid using a “vapor lift”.

  The tower is shown as a stack of low pressure towers 42 located above the high pressure tower 40. However, the present invention is applicable to a configuration in which two towers are arranged or even if the high-pressure tower 40 is stacked on the low-pressure tower 42.

  The method shown in FIG. 4 uses only a single tower section in towers 40 and 42, but optionally there may be more than one section. For example, the low pressure column 42 may have a lower portion between the feed 404 and the reboiler 44 to help concentrate krypton and xenon in the bottom product.

  The approximate L / V ratio of 0.5 that can be used for the basic configuration described above can be higher than necessary to achieve the desired recovery of krypton and xenon. If a portion of the oxygen vapor feedstock 400 to the crude recovery system is fed directly into the lower zone of the low pressure column 42 as an optional stream 401, it will have a lower L / V ratio. The higher the flow rate of the gaseous oxygen feed stream 401 of the low pressure column, the lower the L / V ratio of the column.

  In the case of a pumped liquid oxygen air separation device as shown in FIG. 1, the pumped oxygen is typically vaporized at a single pressure in the main exchanger. However, it is possible to split the pumped liquid oxygen into two streams and vaporize the two streams at slightly different pressures to minimize power costs. Such a configuration takes advantage of the fact that compressed air condenses over a given temperature range (because it is a mixture of gases). There is usually no incentive to take advantage of this possibility, as customers usually do not need two slightly different pressure oxygen products. However, such a possibility is ideally suited to the method of FIG. 4 where a portion of the gaseous oxygen source 401 can be supplied at a slightly lower pressure. Thus, the method shown in FIG. 4 can provide any column L / V ratio up to about 0.5, depending on the flow rate of the optional stream 401 and the quality and / or superheat of the feed stream 400. it can.

  Chill for the tower recovery system is most easily supplied using a liquid oxygen feed stream, but may be heat exchanged with an appropriate stream from the crude recovery system using an external refrigerant. The liquid oxygen refrigerant stream is generally part of the liquid oxygen stream pumped from the main air separation unit and can be sent to any location in the crude product recovery tower system. Nonetheless, the most useful configuration provides liquid oxygen refrigerant to the top of the high pressure column 40 as reflux for this column of stream 410, thereby increasing the flow rate of the reflux stream 402 to the low pressure column 42. It is possible to

  An important advantage of the arrangement shown in FIG. 4 is that it only requires connections for liquid oxygen and gaseous oxygen, and therefore reduces the number of connections to each other, so existing pumped liquid oxygen air separation devices. It is very suitable for remodeling.

  FIG. 5 shows a configuration similar to that shown in FIG. 4, and therefore the same numbers are used in FIG. 5 to represent those that are identical to those in FIG. In the configuration of FIG. 5, there is a reboiler 46 for the high pressure column 40. The heating fluid stream 420 is used to boil the noble gas reduced bottoms liquid in the high pressure column 40, thereby producing a condensed heating fluid stream 422. For example, the heating fluid in stream 420 may be a portion of the compressed air used to vaporize pumped liquid oxygen in the main air separation unit. Since this external heat is applied to the crude product recovery tower system, additional cooling is required compared to the method of FIG. The simplest way to provide this additional cold is by increasing the flow rate of the liquid oxygen refrigerant stream 410. Although stream 410 is shown as being used as reflux for the high pressure column 40, it may alternatively be used as reflux for the low pressure column 42. This additional refrigeration can also be supplied using external refrigeration in a condenser for the low pressure column 42.

  The column L / V ratio in FIG. 4 is limited to approximately 0.5. However, the use of the reboiler 46 in the method of FIG. 5 can result in a larger L / V ratio, mainly depending on the load on the reboiler 46. Such a high L / V ratio can be used to improve krypton recovery when the column operating pressure is very high.

  FIG. 6 shows a configuration of a crude product recovery system including a high pressure column 60, an intermediate pressure column 62 and a low pressure column 66. A reboiler 64 thermally combines columns 60 and 62, and a reboiler 68 thermally combines columns 62 and 66.

  An oxygen feed stream 600 containing higher concentrations of krypton and xenon than in the atmosphere is fed to the lower portion of the high pressure column 60. Stream 600 has a vapor quality of at least 0.9 and is ideally in the gaseous state. In the high-pressure column 60, the separation of the first rare gas-reduced tower top vapor and the first rare gas-enriched tower bottom liquid sent as a raw material stream 604 to the zone below the intermediate pressure tower 62 is performed. Done. The top vapor from the high pressure column 60 is condensed by the reboiler 64. A portion of the resulting condensed stream is used as reflux for the high pressure column 60 and the remaining portion is fed to the low pressure column 66 as reflux for stream 602 (optionally all or a portion of this stream is moderated). It may be sent to the pressure column 62 as reflux). A portion of stream 602 can optionally be withdrawn as a noble gas reduced liquid oxygen product.

  In the intermediate pressure column 62, separation is performed into a tower top vapor in which the second rare gas is reduced and a tower bottom liquid enriched in the second rare gas supplied as the raw material stream 606 to the low pressure tower 66. The reduced top vapor of the second rare gas from the intermediate pressure column 62 is condensed by the reboiler 68. A portion of the resulting condensate stream is used as reflux for the medium pressure column 62 and the remaining portion is fed to the low pressure column 66 as stream 608 reflux. A portion of stream 608 can optionally be withdrawn as a noble gas reduced liquid oxygen product stream 612.

  The low pressure column 66 separates the rare gas depleted vapor withdrawn as product stream 610 into a rare gas enriched liquid product that is withdrawn as stream 620 and can be further purified by known methods. Is called. The cold for this tower system can be supplied by feeding a liquid oxygen stream into this tower system, for example as stream 630 to the top of the high pressure tower 60.

  In general, one third of the vapor condensing in each reboiler is sent as reflux to low pressure column 66 with streams 602 and 608, thereby bringing the L / V ratio to approximately 0.67 in each of the three columns. In order to require such a high L / V ratio to prevent krypton loss, the column operating pressure must be high, for example above about 30 bar. The pressure difference between the three columns tends to be small because the fluid composition on each side is similar for each reboiler. Therefore, problems to be considered regarding the transfer of liquid between the columns can occur. It can be verified that the use of a pump or the introduction of vapors of gaseous oxygen into the liquid transfer line (to achieve a vapor lift) is necessary to effect the liquid transfer.

  These columns are shown with a low pressure column 66 stacked above a medium pressure column 62 above the high pressure column 60. Nonetheless, the present invention applies to a configuration in which the columns are arranged side by side or even if they are stacked differently and the high pressure column 60 is stacked above the low pressure column 66.

  The configuration shown in FIG. 7 is a crude product recovery system that includes two columns 70 and 72 operating at the same pressure. A reboiler 74 is located in the zone below the tower 72. This configuration illustrates how the diameter of the tower of FIG. 3 can be reduced by treating only a portion (generally half) of the main oxygen source containing noble gas in each tower. To do. An oxygen source 700, which is at least predominantly gaseous, is divided between the two towers. Gaseous oxygen stream 702 is fed to a zone below tower 70 where it contacts the refluxing liquid oxygen stream 720 to enrich the reduced gaseous oxygen removed as stream 704 and the rare gas removed as stream 722. To produce a bottom liquid. The remaining portion of the oxygen feed stream 700 is fed to the zone below the column 72 as stream 706. Reflux for column 72 may be provided by a noble gas enriched liquid as stream 722 and / or by a liquid oxygen stream 726 (which may be part of oxygen feed stream 720). . Rather than being used as overhead reflux for column 72, stream 722 may be sent to a zone below column 72 as indicated by stream 724.

  In column 72 is a reboiler 74 operated by a heating fluid 730, 732, which can be a portion of the compressed air used to vaporize pumped liquid oxygen in the main air separation unit. In column 72, the noble gas reduced gaseous oxygen, taken as stream 708, together with the noble gas reduced stream 704, provides a purified oxygen stream 710, and is removed as stream 728 and further in a known manner. Separation takes place into products enriched with noble gases that can be purified.

  Towers 70 and 72 may be separate towers rather than stacked as shown. The reboiler 74 may be external to the tower system, possibly in its own vessel. The tower 70 may have its own reboiler, in which case the noble gas enriched product stream 722 from the tower 70 is combined with the noble gas enriched product stream 728 from the tower 72. May be. Either or both of towers 70 and 72 may have two or more contacts, for example, there may be a lower stage portion of tower 72 below feed stream 706.

  By treating half of the steam feed in each column, the cross section of the column is halved compared to that in FIG.

  The embodiment shown in FIG. 8 is a crude product recovery system including a heat exchanger 80 and a reboiler 84. The exchanger 80 mainly functions as a dephlegmator for producing a tower bottom liquid enriched with a rare gas by bringing the vapor of the cleaning oxygen gas into contact with the descending liquid oxygen. A main oxygen feed stream 800, at least 90% steam, is fed to an upright tube (standpipe) section 80 of the exchanger 80 and travels upward in the exchanger passage. It is partially condensed in this exchanger by heat transfer using the refrigerant streams 830, 832 and the condensate moves downward in the opposite direction to the cleaning gas oxygen in the same exchanger passage. Therefore, defragmentation occurs in the oxygen passage. Liquid oxygen in contact with the cleaning gas oxygen is separated into a top product of gaseous oxygen reduced in noble gas withdrawn as stream 802 and a liquid oxygen tower bottom liquid enriched with noble gas withdrawn as stream 804. To do.

  A portion 808 of the bottom liquid may be part of the heating fluid (this is the portion of the increased air flow used to boil pumped liquid oxygen in the main air separation unit as shown. ) Stream 820, thereby producing a condensed stream 822 that can be reboilered in the reboiler 84. Re-boiling stream 810 (which may be two-phase or all steam) is returned to upright 82. The remaining column bottom liquid 806 can be withdrawn as a product and further purified by known methods. When the oxygen source stream 800 is overheated, the reboiler 84 may be omitted because heat for vaporizing part of the falling liquid is provided by reducing the overheating of the source material.

  The refrigerant streams 830 and 832 do not need to perform heat transfer with the cleaning gas oxygen over the entire length of the exchanger 80. In fact, this heat exchange only takes place in the upper zone of the heat exchanger 80 as shown, so that a higher L / V in the upper zone of the exchanger compared to the case where heat exchange takes place over a longer zone. It is preferred to obtain a ratio. This higher L / V ratio reduces krypton and xenon losses in the upper product gas stream 802. When heat exchange with the refrigerant flow 830 is performed only in the upper zone of the exchanger, the lower zone of the exchanger 80 may form a heat insulating portion of the exchanger 80. Although there is no heat transfer in this area, separation still occurs due to contact between liquid oxygen and gaseous oxygen.

  By introducing liquid oxygen into the gaseous oxygen passage in the upper zone of the exchanger 80, it is possible to substitute for or supplement the refrigerant load. Several methods are known for performing this substitution or replenishment.

  In FIG. 8, because the gaseous upper product stream 802 has just undergone partial condensation by the refrigerant stream 830, it leaves the exchanger 80 as saturated vapor. Stream 802 is generally warmed to ambient temperature by heat exchange with a fluid that is cooled by another exchanger. This additional exchanger may be incorporated as the upper zone of the exchanger 80.

  The configuration shown in FIG. 9 is the same as the configuration of FIG. 8, and therefore the same numbers used in FIG. 9 indicate those corresponding to those of FIG. In FIG. 9, the reboiler 84 of FIG. 8 is incorporated into the lower zone of the exchanger 80, and an upper portion is added to the exchanger 80 to warm the purified gaseous oxygen product in the heating fluid stream 840, 842. Yes.

  The embodiment shown in FIG. 10 is a crude product recovery system including an adsorption container 90. A gaseous oxygen feed stream 900 is passed through the adsorber and a purified oxygen product exits as stream 902. The temperature of stream 900 may be low or ambient. Within the adsorber 90, xenon and / or krypton is adsorbed on one or more adsorbent beds 92. Periodically, the adsorber must be regenerated to recover the adsorbed noble gas components.

  The regeneration process includes depressurization of the adsorption vessel 90 and passing a small amount of regeneration gas 910 (generally nitrogen) through the adsorber. The regeneration outlet stream 920 is enriched with noble gas components that have been desorbed from the adsorbent and can be withdrawn as a product and further purified by known methods. This method of regeneration is well known as pressure swing adsorption (PSA).

  The adsorber 90 can also be regenerated by the well-known temperature swing adsorption (TSA) method. The regeneration stream 910 may be heated with an upstream heater to provide desorption heat for this well-known regeneration method. Alternatively (or in addition) it may be supplied by a heating element located somewhere within the container 90 or by an adsorbent 92.

  FIG. 10 shows a single adsorption vessel 90. Two (or more) vessels can be used, for example, in parallel, to allow the noble gas components to be adsorbed continuously from the feed stream 910.

  Optionally, any of the above figures can include one or more adsorbers to at least partially remove hydrocarbons, carbon dioxide, or nitrous oxide. Such adsorbers can be operated to treat liquid oxygen or gaseous oxygen feed to the recovery system, or intermediate product, or the final gaseous oxygen or liquid oxygen stream of the system.

  As an example of the present invention, a simulation of the method shown in FIG. 1 was performed. In this simulation, a stream enriched in xenon was recovered, and recovery of krypton was not emphasized. The simulation results are shown in Table 1.

  These results indicate that a high xenon recovery rate can be obtained even though the operating pressure is very high and the xenon concentration of the crude product recovery column raw material is low. 15% of the total oxygen feed is used as reflux. The remaining portion of the total oxygen feed is the main tower feed in the form of a slightly superheated steam. The volatility of krypton and xenon is lower at lower pressures, which contributes to reducing the required reflux liquid oxygen flow rate.

  Throughout this specification, the term “means” in relation to means for performing a function is intended to refer to at least one device adapted and / or configured to perform that function. To do.

  The present invention is not limited to the details described above in connection with the preferred embodiments, but numerous modifications and changes are made without departing from the spirit and scope of the invention as defined by the claims. It will be understood that it can.

10 Low pressure column 12, 22 Liquid oxygen pump 14, 24 Heat exchanger 16 Crude noble gas recovery column 18, 28, 38, 44, 46, 64, 68, 74, 84 Reboiler 20 Cold box 26 Crude distillation column 36 Crude krypton And xenon recovery tower 40, 60 high pressure tower 42, 66 low pressure tower 62 medium pressure tower 70, 72 tower 80 heat exchanger 90 adsorption vessel 92 adsorption bed 268 compressor

Claims (54)

A method for recovering at least one rare gas selected from the group consisting of krypton and xenon from a mixture containing oxygen and at least one rare gas selected from the group consisting of krypton and xenon,
Supplying the mixture or a mixture derived therefrom to a rare gas recovery system, and separating the raw material of the mixture in the rare gas recovery system to enrich the rare gas-reduced gaseous oxygen (GOX) and the rare gas To do,
In which at least about 50 mol% of the mixture is supplied to the noble gas recovery system in the gas phase, provided that the mixture raw material is separated by selective adsorption. A rare gas recovery method, wherein the concentration of xenon is 50 times or less the concentration of xenon in air.   The method of claim 1, wherein at least 90 mol% of the mixture feed is a gas.   The method of claim 1, wherein all of the mixture feed is a gas.   The method of claim 1, wherein the noble gas enriched product is enriched with xenon.   The method of claim 1, wherein the noble gas enriched product is enriched with krypton.   The method of claim 1, wherein the noble gas enriched product is enriched in both xenon and krypton.   The method of claim 1, further comprising supplying a stream enriched in xenon to the noble gas recovery system.   8. The method of claim 7, wherein the xenon-enriched stream is at least partially gaseous.   8. The method of claim 7, wherein the xenon enriched stream is a liquid.   The method of claim 1, wherein the mixture is removed from an oxygen pipeline and not pressurized prior to supply to the noble gas recovery system.   The method of claim 1, wherein the pressure of the mixture is increased prior to supply to the noble gas recovery system. Separating the raw air in a cryogenic air separation unit (ASU) to form a nitrogen-rich top vapor and liquid oxygen (LOX);
Pressurizing at least a portion of the liquid oxygen to provide pressurized liquid oxygen; and at least partially evaporating at least a portion of the pressurized liquid oxygen to provide the mixture raw material;
The method of claim 1, further comprising:   The method of claim 12, wherein all of the at least a portion of the pressurized liquid oxygen is vaporized to form the mixture.   The method according to claim 12, wherein the pressure of the mixture raw material is higher than an operating pressure of a portion of the air separation device that produces the liquid oxygen.   13. The method of claim 12, wherein the liquid oxygen stream is divided into at least two parts, each part being vaporized at a different pressure before being fed to the noble gas recovery system.   The method according to claim 1, wherein the rare gas recovery system is a gas-liquid contact separation system, and the method further comprises performing the separation by contacting the mixture raw material with liquid oxygen in the separation system.   The method according to claim 16, wherein the gas-liquid contact separation system is a gas-liquid contact column without a distillation stage, and the method includes separating the mixture raw material through liquid oxygen in the column.   The gas-liquid contact separation system is a distillation system, and the method supplies the mixture to the distillation system to separate the rare gas-reduced gaseous oxygen as the overhead vapor into the rare gas-enriched product. And supplying liquid oxygen as reflux to the distillation system.   The method of claim 18, wherein the mixture is superheated before feeding to the distillation system. Separating raw air into nitrogen-rich overhead vapor and liquid oxygen in a low-temperature air separator;
Removing a flow of liquid oxygen from the air separation device;
Pressurizing at least a portion of this liquid oxygen stream to create a pressurized liquid oxygen stream;
Dividing this flow of pressurized liquid oxygen into a main part and a secondary part,
Providing the mixture by at least partially vaporizing the major portion, and feeding the secondary portion of liquid oxygen as reflux to the distillation system;
The method of claim 18, further comprising:   21. The method of claim 20, wherein all of the major portions are vaporized to form the mixture.   The distillation system comprises a single distillation column, the method feeds the mixture to the column for separation of the noble gas enriched product and the noble gas reduced gaseous oxygen, and a liquid 21. The method of claim 20, comprising feeding the secondary portion of oxygen as reflux to the column. Separating raw air into nitrogen-rich overhead vapor and liquid oxygen in a low-temperature air separator;
Removing a flow of liquid oxygen from the air separation device;
Pressurizing at least a portion of the liquid oxygen stream to create a pressurized liquid oxygen stream;
At least partially evaporating at least a portion of the pressurized liquid oxygen stream to provide the mixture;
Condensing at least a portion of the reduced gaseous oxygen overhead vapor of the noble gas by indirect heat exchange with a refrigerant to produce a condensed overhead product, and at least a portion of the condensed overhead product To the distillation system as reflux,
The method of claim 18, further comprising:   24. The method of claim 23, wherein all of the at least a portion of the pressurized liquid oxygen stream is vaporized to form the mixture.   The distillation system comprises a single distillation column, and the method feeds the mixture to the column for separation of the noble gas enriched product and the noble gas reduced gaseous oxygen; and 24. The method of claim 23, comprising feeding at least a portion of the condensed overhead product to the column as reflux. The distillation system comprises at least a high pressure (HP) distillation column and a low pressure (LP) distillation column, wherein the high pressure and low pressure columns are thermally combined by a reboiler / condenser;
Feeding the mixture to the high pressure column, where it is separated into a noble gas reduced overhead vapor and a noble gas enriched bottom liquid;
Supplying the bottom liquid enriched with a rare gas to the low-pressure column after adjusting the pressure for separation of the rare gas-reduced gaseous oxygen and the rare gas-enriched product;
Condensing at least partially condensed noble gas overhead vapor by indirect heat exchange with a noble gas enriched product to produce at least partially condensed noble gas reduced overhead product;
Supplying at least a portion of the reduced overhead product of the at least partially condensed noble gas to the high pressure column as reflux and liquid from or originating from the high pressure column as reflux to the low pressure column. Supplying,
The method of claim 18 comprising:   27. The method of claim 26, further comprising supplying liquid oxygen as reflux to the high pressure column or the low pressure column.   28. The method further comprises separating the feed air in a cryogenic air separation device into nitrogen-rich overhead vapor and liquid oxygen and using a portion of the liquid oxygen to provide reflux for the liquid oxygen. the method of.   27. The method of claim 26, wherein the high pressure column is reboiling by at least partially evaporating a noble gas enriched bottom liquid by indirect heat exchange with a heating fluid. The distillation system includes at least a high pressure (HP) distillation column, an intermediate pressure (MP) distillation column, and a low pressure (LP) distillation column, the high pressure and intermediate pressure columns being thermally passed through a first reboiler / condenser. And the intermediate and low pressure columns are thermally combined via a second reboiler / condenser, the method comprising:
Feeding the mixture to the high pressure column where it is separated into a first noble gas reduced overhead vapor and a first noble gas enriched bottom liquid;
The intermediate pressure is adjusted after the pressure is adjusted to separate the bottom liquid enriched with the first rare gas into the top vapor reduced in the second rare gas and the bottom liquid enriched in the second rare gas. Feeding to the tower,
Reduction of the first noble gas at least partially condensed by at least partially condensing the reduced top vapor of the first noble gas with indirect heat exchange with the bottom liquid enriched with the second noble gas. Make the top steam,
Supplying at least a portion of the reduced overhead vapor of the at least partially condensed first noble gas to the high pressure column as reflux;
Supplying the liquid from or derived from the high pressure column as reflux to at least one column selected from the low pressure column and the intermediate pressure column;
Supplying the bottom liquid enriched with a second rare gas to the low pressure column for separation into gaseous oxygen depleted in the rare gas and product enriched in the rare gas;
The second noble gas reduced overhead vapor is at least partially condensed by at least partially condensing the second noble gas reduced overhead vapor by indirect heat exchange with the noble gas enriched product. Making,
Supplying at least a portion of the reduced overhead vapor of the at least partially condensed second noble gas to the intermediate pressure column as reflux, and liquid from or derived from the intermediate pressure column to the low pressure Feeding as reflux to the tower,
The method of claim 18 comprising:   31. The method of claim 30, further comprising supplying liquid oxygen as reflux to at least one of the columns.   32. The method of claim 31 further comprising separating the feed air in a cryogenic air separation device into nitrogen-rich overhead vapor and liquid oxygen and using a portion of the liquid oxygen to provide reflux of the liquid oxygen. the method of. The distillation system includes at least a first distillation column and a second distillation column, the first and second columns are operated at the same pressure, and the method comprises:
Feeding the mixture to the first column for separation into noble gas depleted gaseous oxygen and noble gas enriched product;
Feeding the mixture to the second column for separation into noble gas depleted gaseous oxygen and noble gas enriched product;
Supplying liquid oxygen to the first column as reflux, and supplying at least one liquid selected from the group consisting of a product enriched with a rare gas from the first column and liquid oxygen to the second column Feeding as reflux to
The method of claim 18 comprising:   34. The method of claim 33, further comprising dividing the mixture stream into two equal portions and feeding one portion to each column. The gas-liquid contact separation system is at least one heat exchanger, and the method comprises:
Feeding the mixture to the bottom of the one or each heat exchanger;
Providing a condensed mixture by condensing a portion of the mixture rising through the passage of the one or each heat exchanger by indirect heat exchange with a refrigerant; and lowering the mixture rising up in the passage Separation by defragmentation in contact with the condensing mixture
The method of claim 16, further comprising:   36. The method of claim 35, wherein the indirect heat exchange is performed in an upper portion of the one or each heat exchanger.   36. The method of claim 35, wherein the one or each heat exchanger is reboiled by at least partially evaporating the noble gas enriched product by indirect heat exchange with a first heating fluid.   Heat exchange in which the noble gas reduced gaseous oxygen is heated to ambient temperature by indirect heat exchange with a second heating fluid in the one or each heat exchanger and the heat exchange is made into the condensed mixture 36. The method of claim 35, further comprising performing above.   The method of claim 1, wherein the noble gas recovery system is an adsorption system and the method comprises contacting the mixture feedstock with a noble gas selective adsorbent material in the adsorption system.   40. The method of claim 39, wherein the method is selected from the group consisting of a pressure swing adsorption (PSA) method or a temperature swing adsorption (TSA) method.   The method according to claim 1, wherein the concentration of xenon in the mixture raw material is not more than 50 times the concentration of xenon in air.   The method according to claim 1, wherein the concentration of xenon in the mixture raw material is 20 times or less of the concentration of xenon in air.   The method of claim 1, wherein the concentration of xenon in the mixture feed is about 5 times the concentration of xenon in air.   The separation is a crude separation, wherein the product enriched with the noble gas is further processed to be selected from the group consisting of a purified xenon product, a purified krypton product, and a purified krypton and xenon product. The method of claim 1, wherein at least one product is produced. According to claim 1, to recover at least one rare gas selected from the group consisting of krypton and xenon from a pressurized mixture containing oxygen and at least one rare gas selected from the group consisting of krypton and xenon. Equipment,
A low-temperature air separation device for separating the raw air into nitrogen-rich top vapor and liquid oxygen,
A boosting means for boosting at least a portion of the liquid oxygen to provide the boosted liquid oxygen;
Vaporization means for vaporizing at least about 50 mol% of the pressurized liquid oxygen to provide the mixture, and separating the mixture into gaseous oxygen with reduced rare gas and a product enriched with the rare gas Noble gas recovery system,
Noble gas recovery device.   46. The apparatus of claim 45, wherein the rare gas recovery system is a gas-liquid contact tower without a distillation stage for contacting the mixture with liquid oxygen.   46. The apparatus of claim 45, wherein the noble gas recovery system is a distillation system.   A conduit means for supplying a part of the pressurized liquid oxygen from the pressure increasing means to the vaporizing means, and a remaining part of the pressurized liquid oxygen from the pressure increasing means as a reflux to the distillation system 48. The apparatus of claim 47, further comprising further conduit means for performing.   Heat exchange to at least partially condense a portion of the noble gas reduced gaseous oxygen overhead product with a refrigerant to provide at least partially condensed noble gas reduced gaseous oxygen overhead product 48. The apparatus of claim 47, further comprising means and conduit means for feeding at least a portion of the at least partially condensed overhead product as reflux to the distillation system. A first distillation column for separating the mixture into a noble gas-reduced gaseous oxygen and a noble gas enriched product;
A second distillation column for separating the mixture at the same pressure as the first distillation column into a product enriched with rare gas-reduced gaseous oxygen and rare gas,
Pipe line means for supplying liquid oxygen as reflux to at least one of these distillation columns, and at least one selected from the group consisting of products enriched with noble gases from the first distillation column and liquid oxygen A conduit means for supplying the second liquid to the second distillation column,
48. The apparatus of claim 47, further comprising:   46. The apparatus of claim 45, wherein the noble gas recovery system is at least one heat exchanger for separating the mixture by defragmentation.   52. The apparatus of claim 51, further comprising first heat exchange means provided in at least an upper portion of the one or each heat exchanger for condensing the rising mixture by indirect heat exchange with a refrigerant.   52. The apparatus of claim 51, further comprising second heat exchange means provided for vaporizing the product enriched with the noble gas by indirect heat exchange with the first heating fluid.   A third provided above the first heat exchanging means of the one or each heat exchanger in order to warm the gaseous oxygen reduced in rare gas to the ambient temperature by indirect heat exchange with the second heating fluid. 52. The apparatus of claim 51, further comprising a heat exchange means.

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